Complex biologically active molecules are challenging, expensive, and time-consuming to synthesize. Synthesizing compounds with good levels of diastereoselectivity is even more challenging. Doing so generally involves isolating or synthesizing a diasterioenriched intermediate the stereochemistry of which can be preserved in the required subsequent synthetic transformations.
An example of a useful intermediate in the synthesis of a biologically active molecule is (±)-2-(difluoromethyl)-1-(ethoxycarbonyl)cyclopropanecarboxylic acid. In the past, this intermediate was synthesized as shown in Scheme 1, from diethyl 0-2-(difluoromethyl)cyclopropane-1,1-dicarboxylate using a hydrolysis method that yielded modest diastereoselectivity:

There exists a need for new synthetic methods to construct enantioenriched difluoroalkylcyclopropyl and vinylalkylcyclopropyl esters in higher levels of diastereoselectivity.